14 THE SPONGES. 



over to the oxyasters of Lendenfeld, e.g. in Ancorina {Thcnea) fenestrata (0. 

 Sclim.). Til us Vosinaer and Lendenfeld do not agree, and they both differ 

 from Sol las. 



In this matter Topsent (1902) adheres to the terminology of Sollas, and 

 I likewise employ it. That the types singled out from the streptaster 

 series by Sollas exist is of course indisputable. That they also intergrade, 

 cannot be questioned. And this latter fact makes it necessary, whatever 

 technical terms be employed, to describe the spicules of each species. 

 Nevertheless Sollas's subdivision of the strepiasters and his technical terms 

 greatly facilitate reference to the spicules, and also make for accuracy of 

 description. By combining the terms the transitions between the types 

 may in a measure be indicated, e.g. in Poecillasfra cribraria the microscleres 

 of the dermal membrane (Plate 14, Fig. 12 a) are typical spirasters, while 

 those of the parenchyma are plesiastcrs (Plate 14, Yig. 12 b) or plesiaster- 

 metasters (Plate 14, Fig. 12 c, 12 d) and more rarely typical meiastcrs. 



The lists of generic synonymy that are given include references to 

 memoirs in which the genus as a whole is defined or in some way dis- 

 cussed, but are by no means complete guides to the species of the several 

 genera. 



In stating the size of tapering spicule rays, the thickness given is the 

 greatest thickness, unless mention is made to the contrary. 



In the case of some macerated skeletons of Hexactinellids only a direct 

 comparison with types or with determinable specimens could give any 

 warranty for an identification. And even then a doubt, expressed by a 

 query, remains as to the species, although the direct comparison enables one 

 to say that forms agreeing in dictyonal framework with certain described 

 species occur in such a region. 



After having made provisional identifications of the forms included in 

 the collection, I found that before the work could be completed, it would 

 be necessary to examine certain types deposited in European museums. 

 The trustees of the University very kindly granted me leave of absence for 

 the year 1902-03, for which I offer to them and to President Venable my 



